Question

Which solution containing 1 mole of solute dissolved in 1000 grams of water has the lowest freezing point? 1. koh(aq) 2. c2h12o6(aq) 3. c2h5oh(aq) 4. c12h22o11(aq)?

Answer 1

1. KOH, potassium hydroxide, will dissociate into K+ and OH- ions, for a total of two moles of ions in solution. The other three substances are all organic compounds that do not dissociate into separate ions. Freezing point depression is greatest in compounds with the highest (molality * number of ions), so KOH solution will have the lowest freezing point.